A typical roof structure for metal buildings includes a structural support system covered by a plurality of overlapping roof panels. Roof panels are generally formed from sheet materials to define ribs and other contours which provide rigidity and strength to the panels. Mating ribs may be provided where panels overlap for improved interlocking and weather integrity.
As a building heats and cools, the structural support system and the roof panels may experience dimensional changes from thermal expansion and contraction. There is frequently differential movement between the roof panels and underlying structure. Where the roof panels are rigidly fixed to the underlying structure, stresses and physical deformation can be produced in the roof panels, particularly along panel widths perpendicular to the panel ribs.
In a conventional building system, the roof panels are fastened to the underlying structure at low points or valleys in the panel contour. Water run-off and collection also occur along the panel valleys. Thus, the valley locations where fasteners penetrate the roof panels are often the source of water leakage and of roof panel degradation.
A building roof structure may also include an insulating layer between the structural support system and the overlying roof panels. The thickness of the insulating layer may be considerably reduced where the roof panels are fixed to the structure. Compressing the insulating layer thickness greatly decreases the insulating effectiveness of the layer.
U.S. Pat. No. 4,114,338 to Beck teaches a reinforcing plate for use beneath end lapped thin gauge sheets to provide structural support adjacent the joints for improved sealing. The reinforcing plate is elevated above the underlying insulation and is fastened to an underlying purlin through downwardly depending flanges having mounting slots therein. However, there is no provision to assure that the reinforcing plate is not rigidly fixed to the underlying structure. Further, the roofing sheets are fixed to the reinforcing plates along valleys where water run-off and collection can occur.
U.S. Pat. Nos. 4,361,993 and 4,329,823 to Simpson teach a support spacer apparatus for engaging an overlying ribbed panel in a manner to support the panel above the building support structure without compressing the underlying insulation. However, Simpson rigidly fastens the component parts together to provide for structural strength increases.
U.S. Pat. No. 3,332,186 to Cammaert does teach structure for enabling relative movements between corrugated sheet roofing and underlying rafters. Sliding members are fixed to raised corrugations and engage intermittent slideways which are fixed to the rafters to enable relative movements parallel to the corrugations. There is no suggestion about adapting the slider and slideway system to an insulated assembly.
These and other disadvantages in the prior art are overcome by the present invention wherein a subpurlin is provided in a contour effective to support roof panels without compressing underlying insulation while providing elevated fastening support areas and having a clip for slidably fastening the subpurlin to underlying support structure.